Find centers of light spot on a picture?

I have a picture like this:

and I want to find the cordinates of the centers of the light spots.

I am a beginner and I thought to do this thing:

for i = 1:size2
    for j=1:size2
        if(E(i,j)>1)
            f(i,j)=1;
        end
    end
end

where size2 is the dimension of the matrix and E(i,j) is the matrix whose imagesc(E(:,:)) gives the first picture and then applying imfindcircles, but I dont have good results.

How can I do?

Thanks.